CN117889995A - Piezoelectric sensor control method, circuit, piezoelectric sensing system and electronic cigarette - Google Patents
Piezoelectric sensor control method, circuit, piezoelectric sensing system and electronic cigarette Download PDFInfo
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Abstract
The application relates to a piezoelectric sensor control method, a circuit, a piezoelectric sensing system and an electronic cigarette, wherein whether a force removing event occurs to a piezoelectric sensor is monitored; generating a reset signal to control the piezoelectric sensor to reset in response to the force-removing event; when the preset time is reached from the output of the reset signal, the output of the reset signal is stopped to release the reset of the piezoelectric sensor so as to eliminate the rebound voltage.
Description
Technical Field
The application relates to the technical field of piezoelectric sensor control, in particular to a piezoelectric sensor control method, a piezoelectric sensor control circuit, a piezoelectric sensing system and an electronic cigarette.
Background
A piezoelectric sensor, which is a sensor that converts mechanical pressure into an electrical signal, uses the characteristics of a piezoelectric material, and when an external force is applied to the surface thereof, the internal charge distribution changes, thereby generating a voltage. The piezoelectric sensor converts a physical quantity into an electrical signal, and the processing of the electrical signal requires a chip. Therefore, in practical applications, the piezoelectric sensor and the piezoelectric sensor control circuit are generally combined with each other, so as to enhance the function and measurement accuracy of the sensor, and better meet the requirements of different industries.
Fig. 1 is a schematic diagram of a state change of a related art piezoelectric sensor, wherein fig. 1 represents a state change process of the piezoelectric sensor when being stressed. Referring to fig. 1, the piezoelectric sensor is typically a parallel plate-like capacitor structure with uniform positive and negative charges in the medium. Under the condition of no external force, the whole body presents electric neutrality, and when the sensor is stressed, the geometric centers of positive and negative charges are dislocated, so that induced charges are presented on the two polar plates. The greater the force, the greater the degree of misalignment of the geometric centers of the positive and negative charges, and the greater the amount of charge on the plate. If the sensor is subjected to pressure in the opposite direction, charges are generated as well, but the charge sign corresponding to each polar plate is changed according to the direction of the force. The piezoelectric sensor control circuit judges whether a pressure event occurs according to the output voltage.
However, the piezoelectric sensor generally has a charge leakage phenomenon, and the charge leakage can cause the piezoelectric sensor to generate rebound voltage in the process of removing force, so that the control circuit of the piezoelectric sensor can possibly misjudge that a pressure event occurs.
In view of the above problems, the related art provides a solution that converts an output voltage of a piezoelectric sensor into a digital signal by using an analog-to-digital conversion circuit, and then recognizes the digitized "bounce voltage" by using a digital signal processing circuit, thereby preventing misjudgment and correctly performing pressure event judgment. The main problem of this scheme is that, on the one hand, the analog-to-digital conversion circuit is relatively complex, and the circuit area overhead and the power consumption overhead are both large, resulting in high design and use costs. On the other hand, in order to match with the analog-digital conversion circuit, the digital signal processing circuit connected with the analog-digital conversion circuit is complex, and the design and use cost are also brought.
Aiming at the problem of high control cost of the piezoelectric sensor in the related technology, no effective solution is proposed at present.
Disclosure of Invention
In view of the foregoing, it is desirable to provide a piezoelectric sensor control method, a circuit, a piezoelectric sensing system, and an electronic cigarette that can reduce control costs.
In a first aspect, the present application provides a piezoelectric sensor control method, including:
Monitoring whether a force-removing event occurs to the piezoelectric sensor, wherein the force-removing event indicates that the pressure born by the piezoelectric sensor is gradually reduced;
generating a reset signal to control the piezoelectric sensor to reset in response to the force-removing event;
And stopping outputting the reset signal to release the reset of the piezoelectric sensor when the preset time is reached from the time of outputting the reset signal.
In some of these embodiments, generating a reset signal to control the piezoelectric sensor to reset in response to the force-withdrawal event comprises:
Detecting an output voltage of the piezoelectric sensor;
outputting a second signal when the output voltage of the piezoelectric sensor is detected to be greater than a voltage threshold, wherein the voltage threshold is a voltage capable of representing that the piezoelectric sensor detects a pressure event;
The reset signal is generated in response to a level flip of the second signal.
In some of these embodiments, the preset time is not less than a drain time of residual charge in the piezoelectric sensor that can trigger a pressure event.
In some embodiments, stopping outputting the reset signal from outputting the reset signal until reaching a preset time includes:
Counting a clock signal in response to the reset signal;
and stopping outputting the reset signal when the counted clock number reaches a preset value, wherein the preset value is determined based on the preset time and the clock period of the clock signal.
In a second aspect, the present application provides a piezoelectric sensor control circuit comprising: the device comprises a comparison unit, a logic unit and a reset switch, wherein the logic unit comprises a trigger and a counter; the output end of the comparison unit is connected with the clock input end of the trigger, the output end of the trigger is connected with the reset switch, the clock input end of the counter is used for inputting a clock signal, the output end of the counter is connected with the reset end of the trigger, and the enabling end of the counter is connected with the output end of the trigger;
The comparison unit is used for receiving the output voltage of the piezoelectric sensor and comparing the output voltage of the piezoelectric sensor with a voltage threshold representing the occurrence of a pressure event;
the trigger is used for responding to the comparison result output by the comparison unit and outputting a reset signal;
the counter is used for responding to the clock signal, counting the clock signal and controlling the trigger to reset when the counted clock number reaches a preset value;
and the reset switch is connected with the piezoelectric sensor and is used for responding to the reset signal to reset the piezoelectric sensor.
In some of these embodiments, the logic unit further comprises: and the input end of the inverter is connected with the output end of the comparison unit, and the output end of the inverter is connected with the clock input end of the trigger.
In some embodiments, a first end of the reset switch is connected with a voltage output pin of the piezoelectric sensor, a second end of the reset switch is connected with a reference voltage input pin of the piezoelectric sensor, and a third end of the reset switch is connected with an output end of the trigger; the working state of the reset switch comprises that the first end of the reset switch is connected with the second end or the third end.
In some embodiments, the comparing unit includes a first comparator and a second comparator, and the piezoelectric sensor control circuit includes a first logic unit, a second logic unit, and an or gate; the output end of the first comparator is connected with the input end of the first logic unit, the output end of the second comparator is connected with the input end of the second logic unit, and the output ends of the first logic unit and the second logic unit are connected with the input end of the OR gate; the output end of the OR gate is connected with the reset switch; wherein,
The first logic unit is used for responding to the forward output voltage of the piezoelectric sensor, and the second logic unit is used for responding to the reverse output voltage of the piezoelectric sensor.
In a third aspect, the present application provides a piezoelectric sensing system comprising: a piezoelectric sensor and the piezoelectric sensor control circuit according to the second aspect, wherein the piezoelectric sensor is connected to the piezoelectric sensor control circuit.
In a fourth aspect, the present application provides an electronic cigarette, comprising: the piezoelectric sensor and the piezoelectric sensor control circuit of the second aspect are arranged on the main body, and the piezoelectric sensor is connected with the piezoelectric sensor control circuit.
According to the piezoelectric sensor control method, the circuit, the piezoelectric sensing system and the electronic cigarette, whether a force removing event occurs to the piezoelectric sensor is monitored; generating a reset signal to control the piezoelectric sensor to reset in response to the force-removing event; when the preset time is reached from the output of the reset signal, the output of the reset signal is stopped to release the reset of the piezoelectric sensor so as to eliminate the rebound voltage.
The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below to provide a more thorough understanding of the other features, objects, and advantages of the application.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments or the conventional techniques of the present application, the drawings required for the descriptions of the embodiments or the conventional techniques will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.
FIG. 1 is a schematic diagram of a state change of a piezoelectric sensor according to the related art when the piezoelectric sensor is stressed;
FIG. 2 is a schematic diagram of an equivalent circuit of a single-ended piezoelectric sensor;
FIG. 3 is a schematic diagram of a response curve of a single-ended piezoelectric sensor;
FIG. 4 is a flow chart of a method of piezoelectric sensor control in one embodiment;
FIG. 5 is a schematic diagram of a piezoelectric sensor control method according to one embodiment;
FIG. 6 is a schematic diagram of the architecture of a piezoelectric sensor control circuit in one embodiment;
FIG. 7 is a diagram showing the internal structure of the logic cell of FIG. 6;
FIG. 8 is a schematic diagram of a piezoelectric sensor control circuit in another embodiment;
FIG. 9 is a diagram showing the internal structure of the logic cell of FIG. 8;
FIG. 10 is a schematic diagram of an alternative configuration of a trigger in one embodiment;
FIG. 11 is a schematic diagram of an equivalent circuit of a dual-ended piezoelectric sensor;
FIG. 12 is a schematic diagram of a piezoelectric sensor control circuit in another embodiment;
FIG. 13 is a diagram showing the transition of the state of operation of the logic unit to control the on/off of the reset switch in one embodiment;
FIG. 14 is a waveform diagram of the effects achieved by the piezoelectric sensor control circuit in one embodiment;
fig. 15 shows a schematic diagram of the working principle of the logic unit in fig. 9.
Reference numerals illustrate: 1. a piezoelectric sensor control circuit; 11. a comparison unit; 111. a first comparator; 112. a second comparator; 12. a logic unit; 121. a trigger; 122. a counter; 123. an inverter; 12a, a first logic unit; 12b, a second logic unit; 121a, a first trigger; 122a, a first counter; 123a, a first inverter; 13. A first pin; 14. a second pin; 15. a third pin; 16. an amplifying unit; 17. a voltage generation module; 18. or gate.
Detailed Description
In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Embodiments of the application are illustrated in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that the terms first, second, etc. as used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element. For example, a first resistance may be referred to as a second resistance, and similarly, a second resistance may be referred to as a first resistance, without departing from the scope of the application. Both the first resistor and the second resistor are resistors, but they are not the same resistor.
It is to be understood that in the following embodiments, "connected" is understood to mean "electrically connected", "communicatively connected", etc., if the connected circuits, modules, units, etc., have electrical or data transfer between them.
It is understood that "at least one" means one or more and "a plurality" means two or more. "at least part of an element" means part or all of the element.
As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and/or the like, specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof. Also, the term "and/or" as used in this specification includes any and all combinations of the associated listed items.
Fig. 2 is a schematic diagram of an equivalent circuit of a single-ended piezoelectric sensor. As shown in fig. 2, where MEMS represents a piezoelectric sensor, which may be equivalently referred to as a charge source q, a capacitor Cp, and a resistor Rp are connected in parallel with each other, vout represents an output voltage of the piezoelectric sensor, and Vref represents a reference voltage of the piezoelectric sensor. When the plate is pressed, the charge source q generates a charge and stores it in the capacitor Cp, forming a voltage difference of Vout-vref=q/Cp, however, due to the resistor Rp, the charge on the capacitor Cp slowly leaks through Rp, resulting in a decrease in the charge amount on the second Cp of the capacitor, and thus the value of Vout-Vref decreases until vout=vref, where the charge is 0.
Fig. 3 is a schematic diagram of a response curve of a single-ended piezoelectric sensor. As shown in fig. 3, when a counter pressure is applied to the piezoelectric sensor (e.g., to the lower plate of fig. 1), an electrical charge is generated on the plate, forming a voltage; as the force increases, the amount of charge increases and the output voltage Vout increases. The output voltage Vout peaks when the force just changes from increasing to remaining unchanged. Subsequently, the output voltage Vout slowly decreases due to the aforementioned charge leakage. If the "force-withdrawing process" occurs before the charge is completely leaked, the charges with opposite signs are generated inside the piezoelectric sensor, so that the charges generated in the "force-withdrawing process" are counteracted, and the steep force-withdrawing edge and the rebound voltage are shown on the output voltage. The rebound voltage is a voltage formed by the residual charge on the capacitor Cp after the residual charge generated by the "force removing process" and the residual charge generated by the "force removing process start time" have been cancelled. With the slow leakage of the residual charge, the rebound voltage is gradually restored to the baseline potential (the schematic is shown as 0 potential for convenience). Similarly, when a positive pressure is applied to the sensor (e.g., the top plate of fig. 1 is forced), the above-mentioned four processes of voltage peak with increasing force, charge leakage with stable force maintenance, voltage drop, rebound voltage when the force is removed, and slow recovery of the rebound voltage are still experienced.
Normally (irrespective of the rebound voltage), a pressure event means that the output voltage of the piezoelectric sensor is not less than the voltage threshold. Whether the positive pressure event or the negative pressure event is judged, whether the output voltage is larger than a voltage threshold value or not is only needed to be detected, and if so, the pressure event is judged to occur. The voltage threshold determination herein refers to comparing the voltage amplitude, regardless of the direction. As for the direction of application of force, it can be determined by comparing the magnitude of the output voltage with the baseline voltage. However, if the amplitude of the rebound voltage generated during the force removal process exceeds the judgment threshold value of the pressure event, the pressure event is mistakenly considered to occur. That is, the bounce voltage will likely trigger a false determination, resulting in the piezoelectric sensor control circuit "mistaking" that pressure has occurred. For example, industrial equipment false-start, medical equipment false-alarm, and electronic cigarette false-ignition, which can cause inconvenience and even safety hazards.
Based on the above analysis, in one embodiment, a piezoelectric sensor control method is provided. Fig. 4 is a flowchart of the piezoelectric sensor control method of the present embodiment, as shown in fig. 4, the flowchart including the steps of:
step S401, monitoring whether a force-removing event occurs to the piezoelectric sensor, wherein the force-removing event indicates that the pressure born by the piezoelectric sensor is gradually reduced;
Step S402, in response to a force-removing event, generating a reset signal to control the piezoelectric sensor to reset;
Step S403, when the preset time is reached from the output of the reset signal, the output of the reset signal is suspended to release the reset of the piezoelectric sensor.
The force removing event is reflected by gradual reduction of the pressure born by the piezoelectric sensor. The piezoelectric sensor is controlled to reset, namely the voltage output pin of the piezoelectric sensor and the reference voltage input pin are short-circuited, namely Vout=Vref is forced, and the charge of the piezoelectric sensor is discharged, so that the rebound voltage is reduced. The preset time is reset maintaining time of the piezoelectric sensor, namely resetting is released after the piezoelectric sensor is reset for a period of time. Preferably, the preset time is not less than the discharge time of the residual charge in the piezoelectric sensor that can trigger the pressure event, thus ensuring that the charge corresponding to the rebound voltage is discharged.
In the steps S401 to S403, considering that the rebound voltage occurs following the force-removing event, when the force-removing event is detected, the piezoelectric sensor is immediately controlled to reset, and the reset is released after the preset time is maintained, so as to release a certain amount of charge, thereby reducing the rebound voltage and avoiding false triggering of the pressure event due to the rebound voltage. The method can be realized by adopting an asynchronous circuit structure, avoids the adoption of an analog-to-digital conversion circuit and a digital signal processing circuit, and reduces the control cost of the piezoelectric sensor.
In one embodiment, a method of determining a withdrawal event is provided. Detecting the output voltage of the piezoelectric sensor; when the output voltage of the piezoelectric sensor is detected to be converted from a first voltage area to a second voltage area, judging that the piezoelectric sensor generates a force removing event; the voltage of the first voltage area is not smaller than the voltage threshold value, and the voltage of the second voltage area is smaller than the voltage threshold value. FIG. 5 is a schematic diagram of a piezoelectric sensor control method, please refer to FIG. 5, wherein V1 represents a first threshold voltage for detecting a positive pressure event; v2 represents a second threshold voltage for detecting a reverse pressure event; the first threshold voltage V1 and the second threshold voltage V2 are equal in magnitude and opposite in direction. The first threshold voltage V1 and above is defined as a region a, the second threshold voltage V2 and below is defined as a region C, and both the region a and the region C belong to the first voltage region. The portion between the first threshold voltage V1 and the second threshold voltage V2 is defined as a region B, and the region B is the second voltage region. A force withdrawal event may be considered to occur when it is detected that the output voltage of the piezoelectric sensor exhibits a transition from a first voltage region (region a or region C) to a second voltage region (region B). For example, for a forward pressure event, the process of Vout exceeding V1 is considered to be forced, and the process of Vout changing from greater than V1 to less than V1 is considered to be de-forced. Similarly, the reverse pressure event can also be determined by the process of Vout going up and down over V2 to determine whether force is applied or removed.
To further disclose the effect of the piezoelectric sensor control method, please continue to refer to fig. 5. The transition of the output voltage of the piezoelectric sensor between the area A, the area B and the area C is monitored in real time. When the transition from region a to region B occurs, the piezoelectric sensor is reset, the charge on the piezoelectric sensor capacitance is quickly discharged, and the reset action is maintained for a preset time, and then the reset is automatically canceled. Similarly, when the transition from region C to region B occurs, the piezoelectric sensor is reset, rapidly bleeding off the charge on the piezoelectric sensor capacitance, and the reset action is maintained for a preset time, and then the reset is automatically revoked.
In this embodiment, on the one hand, when the force-removing action occurs, since the piezoelectric sensor is reset in time and the charge is continuously discharged for a period of time, the charge corresponding to the rebound voltage to be generated is continuously and rapidly discharged in the period of time, so that the rebound voltage cannot be formed, and false triggering cannot be caused. On the other hand, thanks to the detection mechanism of the three areas of the proposed method, the piezoelectric sensor will not reset in the time of responding to the force application process, and will only reset when it senses the force-releasing action, so that its normal working function will not be affected.
In one embodiment, a piezoelectric sensor control circuit is provided for implementing the piezoelectric sensor control method of the above embodiment. Fig. 6 is a schematic structural diagram of a piezoelectric sensor control circuit of the present embodiment, and fig. 7 shows an internal structural diagram of the logic unit in fig. 6. Referring to fig. 6 and 7, the piezoelectric sensor control circuit 1 includes: the comparing unit 11, the logic unit 12, and the reset switch K, the logic unit 12 includes a flip-flop 121 and a counter 122. The output end of the comparison unit 11 is connected with the clock input end CK1 of the trigger 121, the output end Q of the trigger is connected with the reset switch K, the clock input end CK2 of the counter 122 is used for inputting a clock signal, the output end of the counter 122 is connected with the reset end Rst of the trigger 121, and the enable end EN of the counter 122 is connected with the output end Q of the trigger 121.
A comparison unit 11 for receiving the output voltage of the piezoelectric sensor and comparing the output voltage of the piezoelectric sensor with a voltage threshold value indicative of the occurrence of a pressure event.
A flip-flop 121 for outputting a reset signal in response to the comparison result output from the comparison unit 11.
A counter 122 for counting the clock signal in response to the clock signal, and controlling the flip-flop 121 to be reset when the counted number of clocks reaches a preset value.
And the reset switch K is connected with the piezoelectric sensor and is used for responding to a reset signal to reset the piezoelectric sensor.
In this embodiment, the logic unit 12 controls the reset switch K to be closed, so as to quickly discharge the charge in the capacitor Cp. Since the piezoelectric sensor continuously generates charges during the force removal process, the reset process needs to be maintained for a first preset time, which is longer than the duration that the rebound voltage exceeds V1, so as to ensure that the charges continuously generated during the force removal process of the piezoelectric sensor do not cause the rebound voltage of the piezoelectric sensor to exceed V1 again.
According to the piezoelectric sensor control circuit, on one hand, the output voltage of the piezoelectric sensor can be subjected to post-processing so as to meet the actual application requirements. On the other hand, the piezoelectric sensor control circuit monitors whether a force-removing event occurs to the piezoelectric sensor when the force-removing event occurs in the process of executing the piezoelectric sensor control method, wherein the force-removing event indicates that the pressure born by the piezoelectric sensor is gradually reduced; generating a reset signal to control the piezoelectric sensor to reset in response to the force-removing event; and stopping outputting the reset signal to release the reset of the piezoelectric sensor when the preset time is reached from the time of outputting the reset signal, so that the probability of false triggering of the pressure event is reduced. Reference may be made to the above embodiments for further principles and effects of the piezoelectric sensor control method, which are not described herein.
Optionally, the piezoelectric sensor control circuit 1 further comprises a first pin 13, a second pin 14, and a third pin 15. The first pin 13 is used for being connected with a voltage output pin Vout of the piezoelectric sensor, the second pin 14 is used for being connected with a reference voltage input pin Vref of the piezoelectric sensor, the third pin 15 is used as a signal output end of the whole piezoelectric sensor control circuit, and the meaning represented by an output signal is determined by application requirements.
Alternatively, the piezoelectric sensor control circuit 1 may also be provided with an amplifying unit 16 and a voltage generating module 17. An amplifying unit 16 is connected between the first pin 13 and the comparing unit 11 for amplifying the output voltage of the piezoelectric sensor and improving the driving capability. The amplifying unit 16 may be implemented with a buffer amplifier, a single-ended amplifier, a differential amplifier, or a programmable gain amplifier. The voltage generating module 17 is connected to the second pin 14 and is responsible for providing a dc bias to the piezoelectric sensor. The voltage generating module 17 can be selected and removed according to the application requirement, and at this time, the reference voltage input pin Vref of the piezoelectric sensor can be grounded according to the application requirement.
In one embodiment, a first end of the reset switch K is connected to the voltage output pin Vout of the piezoelectric sensor, a second end of the reset switch K is connected to the reference voltage input pin Vref of the piezoelectric sensor, and a third end of the reset switch K is connected to the output Q of the trigger 121; the working state of the reset switch K comprises that the first end of the reset switch K is connected with the second end or the third end.
In one embodiment, with continued reference to fig. 7, the logic unit 12 further includes an inverter 123, an input terminal of the inverter 123 is connected to the output terminal of the comparing unit 11, and an output terminal of the inverter 123 is connected to the clock input terminal CK1 of the flip-flop 121.
In fig. 6, a comparison unit 11 is used to detect either a forward pressure event or a reverse pressure event. In some of these embodiments, fig. 8 provides a schematic diagram of another piezoelectric sensor control circuit for detecting both a forward pressure event and a reverse pressure event, and fig. 9 shows an internal structure diagram of the logic unit in fig. 8. As shown in fig. 8, the comparison unit 11 includes a first comparator 111 and a second comparator 112 on the basis of fig. 6. As shown in fig. 9, the piezoelectric sensor control circuit includes a first logic unit 12a, a second logic unit 12b, and an or gate 18. The output end of the first comparator 111 is connected with the input end of the first logic unit 12a, the output end of the second comparator 112 is connected with the input end of the second logic unit 12b, and the output ends of the first logic unit 12a and the second logic unit 12b are connected with the input end of the or gate 18; the output of the or gate 18 is connected to a reset switch K. Wherein the first logic unit 12a is configured to respond to a forward output voltage of the piezoelectric sensor and the second logic unit 12b is configured to respond to a reverse output voltage of the piezoelectric sensor. The first comparator 111 is provided with a first threshold voltage V1 for detecting a forward pressure event; a second threshold voltage V1 is provided in the second comparator 112 for detecting a reverse pressure event. The voltage thresholds corresponding to the two comparators are V1 and V2 in fig. 5, respectively. If the application scene only needs to detect the pressure in one direction, the signal processing circuit formed by one group of comparators and logic units can be omitted according to the requirement.
In this embodiment, the piezoelectric sensor control circuit includes two logic units, each logic unit is responsible for processing the output of one comparator, the outputs of the two logic units are respectively used as two inputs of the or gate, and the output of the or gate is used as the reset signal of the MEMS. Each logic cell in turn includes an Inverter (INV), a D flip-flop (DFF), and a Counter (CNT). The input of the inverter is the output of the front-stage comparator, the input of the counter is a clock signal, the output of the inverter is connected with the clock end CK1 of the D trigger, the D end of the D trigger is connected with the VDD, the reset end of the D trigger is connected with the output of the counter, and the Q end of the D trigger is used as an enabling signal of the counter and is also used as the output of the corresponding logic unit. The logic unit of the embodiment combines the design methods of the synchronous circuit and the asynchronous handshake circuit, and can complete MEMS reset logic with little hardware area cost and power consumption cost, thereby avoiding the adoption of an analog-digital conversion circuit and a digital signal processing circuit and reducing the control cost of the piezoelectric sensor.
The D flip-flop shown in fig. 9 is but one alternative, in some of which the D flip-flop may be obtained by other types of flip-flop and logic gate combinations. For example, referring to fig. 10, the RS flip-flop or JK flip-flop can be changed to a "D flip-flop" in combination with an inverter.
The piezoelectric sensor control circuit provided by the embodiment can be used for controlling the single-end piezoelectric sensor. In practical applications, piezoelectric sensors that output at both ends of the differential may also be present, and for this case, the circuit configuration of fig. 6 or fig. 8 need only be changed to a circuit that processes differential signals. In one embodiment, FIG. 11 presents a schematic diagram of an equivalent circuit of a dual-ended piezoelectric sensor. Accordingly, fig. 12 provides a schematic structural diagram of another piezoelectric sensor control circuit, as shown in fig. 12, on the basis of fig. 8, two reset switches, namely, a first reset switch K1 and a second reset switch K2, are provided for resetting the two-terminal outputs Voutp and Voutn. The amplifying unit 16 amplifies the differential output signal of the piezoelectric sensor.
The working principle of the piezoelectric sensor control circuit provided in the above embodiments will be further described below.
Fig. 13 is a switching diagram of the working state of the logic unit for controlling the on-off of the reset switch. As shown in fig. 13, the three voltage regions A, B, C in fig. 5 are divided by the first comparator 111 and the second comparator 112 to complete detection. The logic unit encodes the circuit states corresponding to the three areas respectively, wherein the voltage area A corresponds to the state code 00, the voltage area B corresponds to the state code 01, the area C corresponds to the state code 10, when the conversion from the area A to the area B occurs, the reset action is triggered, the logic unit controls the reset switch to be closed, the reset switch needs to be continued for a set period of time, and then the reset switch is automatically withdrawn, namely the reset switch is opened. Similarly, when the transition from the area C to the area B occurs, the reset action is triggered, and the logic unit controls the reset switch to be turned on, and the reset switch needs to be automatically withdrawn after a set period of time. In other state transitions, such as region B to region a, or region B to region C, the logic unit does not control the reset switch.
Fig. 14 is a waveform diagram showing the effect achieved by the piezoelectric sensor control circuit. As shown in fig. 14, when the first comparator 111 and the second comparator 112 indicate the "force-removing state", the reset signals are generated respectively, and the reset signals are automatically removed after a period of time. Note that the logic shown in the figures is defined as: the input voltage of the first comparator 111 is output as a high level when the input voltage is greater than the first threshold voltage V1, the input voltage of the second comparator 112 is output as a high level when the input voltage is less than the second threshold voltage V2, and the reset signal is defined as positive logic, that is, the output of the high level indicates that the reset operation occurs. The above definition can be freely defined according to the specific design condition of the piezoelectric sensor control circuit, and the definition mode in the figure is only one kind of display example.
Fig. 15 is a schematic diagram illustrating the working principle of the logic unit in fig. 9, and as shown in fig. 15, taking the first logic unit 12a as an example, when the first comparator 111 generates a falling edge representing the force-removing action, it passes through the first inverter 123a and is converted into a rising edge. This rising edge is then input to the clock input CK1 of the first flip-flop 121a, triggering the Q of the first flip-flop 121a to pull high from logic 0 to logic 1. Next, the Q-terminal logic 1 of the first flip-flop 121a is used as the enable signal EN of the first counter 122a to trigger the enabling operation of the first counter 122 a. The first counter 122a starts counting the clock signal, and when the count reaches a preset value, the output of the first counter 122a is pulled up from logic 0 to logic 1. And the logic 1 signal serves as a RST reset signal for the first flip-flop 121a, resetting the first flip-flop 121a, pulling its Q terminal from logic 1 low to logic 0. Since the Q-terminal of the first flip-flop 121a is again the enable EN of the first counter 122a, the first counter 122a then enters an disabled state in which the output of the first counter 122a is pulled down from logic 1 to logic 0. Since the output of the first counter 122a is the RST reset signal of the first flip-flop 121a, the continuous reset of the first flip-flop 121a is canceled at this time. Thus, the first counter 122a and the first trigger 121a return to the initial state, and the whole circuit will meet the output falling edge of the next comparator.
In the above process, the Q-terminal signal output by the first flip-flop 121a is a square wave. The rising edge of the square wave follows the falling edge of the output of the first comparator 111, and the duration of the square wave is determined by the count value of the first counter 122a and the frequency of the clock signal. The square wave is used as a part of an MEMS reset signal and is responsible for controlling a reset switch K to reset the MEMS in the process of removing force after the MEMS receives force in a certain direction. The two logic units respectively process the output of the two comparators, and the final MEMS reset signal is obtained by OR gate operation of the output results of the two logic units.
It should be noted that the rising edge, the falling edge, the logic 0, the logic 1, etc. of the design are not fixed, and may be freely determined according to the design habit of the designer. In some embodiments, the CK terminal of the D flip-flop may be defined as a falling edge trigger, and if so defined, no inverter is required, and the falling edge of the comparator is directly connected to the CK terminal of the D flip-flop. For another example, in some embodiments, it may be defined that the RST end of the D flip-flop is reset by a logic 0, and then the counter must output a logic 0 after the count reaches the preset value, or an inverter is connected to the counter to convert the positive logic output of the counter to the negative logic output.
If the force in the positive and negative directions born by the MEMS is not required to be detected in the practical application, only one direction of force is required to be detected, the logic unit does not need an OR gate, and only one logic unit and one comparator are required.
In addition, the piezoelectric sensor control circuit provided by the embodiment can be integrated into a chip, the hardware area cost and the power consumption cost are fully considered, the misjudgment influence caused by the rebound voltage of the piezoelectric sensor can be eliminated with the smaller circuit area cost and the smaller power consumption cost, the use of an analog-digital conversion circuit is avoided, and the design of a complex digital signal processing circuit is also avoided. It will be appreciated that the piezoelectric sensor control circuit described above may take other forms as well, and is not limited to the form already mentioned in the above embodiment, as long as it is capable of achieving the rebound voltage cancellation function.
In one embodiment, a piezoelectric sensing system is provided that includes a piezoelectric sensor and a piezoelectric sensor control circuit, the piezoelectric sensor being coupled to the piezoelectric sensor control circuit. The piezoelectric sensor converts the physical quantity into an electrical signal, and the processing of the electrical signal can be accomplished by a piezoelectric sensor control circuit. The piezoelectric sensor control circuit can reduce rebound voltage and periodically reset the piezoelectric sensor to inhibit baseline voltage from rising, so that false triggering of pressure event is avoided, and the reliability of the piezoelectric sensing system is improved. The piezoelectric sensing system can be widely applied to various fields, including but not limited to: industrial automation, piezoelectric sensors can be used to measure the execution dynamics of the robot terminal actuators to ensure that they operate accurately; the medical equipment, the piezoelectric sensor can be used for measuring physiological parameters such as blood pressure, respiratory rate, heartbeat rate and the like; the piezoelectric sensor can be used for measuring the weight and pressure distribution of the vehicle in the automobile industry, providing data support for the design of the vehicle and monitoring the systems such as an air bag, a brake and the like; air quality detection, piezoelectric sensors can be used to measure pressure and humidity in the air, thereby helping to detect harmful gases in the air; the piezoelectric sensor can be used for monitoring the structural safety and stability of a building and measuring the vibration conditions of structures such as bridges, tunnels and the like; consumer electronics, such as electronic cigarettes, piezoelectric sensors may be used to detect a smoking or blowing action, triggering a function switch of the electronic cigarette.
In one embodiment, an electronic cigarette is provided that includes a body configured with a piezoelectric sensor, the body further configured with a piezoelectric sensor control circuit as described above, or integrated with a chip including a piezoelectric sensor control circuit as described above, or configured with a piezoelectric sensing system as described above. Optionally, the main body further comprises a PCB motherboard, and the piezoelectric sensor is disposed on the PCB motherboard.
In the description of the present specification, reference to the term "some embodiments," "other embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of the application should be assessed as that of the appended claims.
Claims (10)
1. A piezoelectric sensor control method, comprising:
Monitoring whether a force-removing event occurs to the piezoelectric sensor, wherein the force-removing event indicates that the pressure born by the piezoelectric sensor is gradually reduced;
generating a reset signal to control the piezoelectric sensor to reset in response to the force-removing event;
And stopping outputting the reset signal to release the reset of the piezoelectric sensor when the preset time is reached from the time of outputting the reset signal.
2. The method of claim 1, wherein generating a reset signal to control the piezoelectric sensor to reset in response to the force-withdrawal event comprises:
Detecting an output voltage of the piezoelectric sensor;
outputting a second signal when the output voltage of the piezoelectric sensor is detected to be greater than a voltage threshold, wherein the voltage threshold is a voltage capable of representing that the piezoelectric sensor detects a pressure event;
The reset signal is generated in response to a level flip of the second signal.
3. The piezoelectric sensor control method of claim 1, wherein the preset time is not less than a bleed-off time of residual charge in the piezoelectric sensor that can trigger a pressure event.
4. The piezoelectric sensor control method according to claim 1, wherein suspending outputting the reset signal from when the reset signal is output to when a preset time is reached, comprises:
Counting a clock signal in response to the reset signal;
and stopping outputting the reset signal when the counted clock number reaches a preset value, wherein the preset value is determined based on the preset time and the clock period of the clock signal.
5. A piezoelectric sensor control circuit, comprising: the device comprises a comparison unit, a logic unit and a reset switch, wherein the logic unit comprises a trigger and a counter; the output end of the comparison unit is connected with the clock input end of the trigger, the output end of the trigger is connected with the reset switch, the clock input end of the counter is used for inputting a clock signal, the output end of the counter is connected with the reset end of the trigger, and the enabling end of the counter is connected with the output end of the trigger;
The comparison unit is used for receiving the output voltage of the piezoelectric sensor and comparing the output voltage of the piezoelectric sensor with a voltage threshold representing the occurrence of a pressure event;
the trigger is used for responding to the comparison result output by the comparison unit and outputting a reset signal;
the counter is used for responding to the clock signal, counting the clock signal and controlling the trigger to reset when the counted clock number reaches a preset value;
and the reset switch is connected with the piezoelectric sensor and is used for responding to the reset signal to reset the piezoelectric sensor.
6. The piezoelectric sensor control circuit of claim 5 wherein the logic unit further comprises: and the input end of the inverter is connected with the output end of the comparison unit, and the output end of the inverter is connected with the clock input end of the trigger.
7. The piezoelectric sensor control circuit of claim 5, wherein a first end of the reset switch is connected to a voltage output pin of the piezoelectric sensor, a second end of the reset switch is connected to a reference voltage input pin of the piezoelectric sensor, and a third end of the reset switch is connected to an output of the trigger; the working state of the reset switch comprises that the first end of the reset switch is connected with the second end or the third end.
8. The piezoelectric sensor control circuit of claim 5, wherein the comparison unit comprises a first comparator and a second comparator, the piezoelectric sensor control circuit comprising a first logic unit, a second logic unit, and an or gate; the output end of the first comparator is connected with the input end of the first logic unit, the output end of the second comparator is connected with the input end of the second logic unit, and the output ends of the first logic unit and the second logic unit are connected with the input end of the OR gate; the output end of the OR gate is connected with the reset switch; wherein,
The first logic unit is used for responding to the forward output voltage of the piezoelectric sensor, and the second logic unit is used for responding to the reverse output voltage of the piezoelectric sensor.
9. A piezoelectric sensing system, comprising: a piezoelectric sensor and the piezoelectric sensor control circuit of any one of claims 5 to 8, the piezoelectric sensor being connected to the piezoelectric sensor control circuit.
10. An electronic cigarette, comprising: a main body on which a piezoelectric sensor and the piezoelectric sensor control circuit of any one of claims 5 to 8 are provided, the piezoelectric sensor being connected to the piezoelectric sensor control circuit.
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